The packaging laminating material that has rich in plasticity has been used for packaging liquid food over many years.
The packaging container for cow's milk, juice, sake, white distilled liquor, mineral water, and other drinks is manufactured according to,
for example, forming the web shape creased packaging material of fibrous substrate (for example, paper etc.)/plastics laminate by longitudinal sealing to an elongated direction at the tube shape,
                filling a product to be filled in the packaging material formed by the tube shape,        transversal sealing tube shape packaging material in the transversal direction,        forming in the primary shape of a cushion or a pillow,        cutting at fixed spacing at an individual container,        folding up along with crease lines and forming in the final shape.        
The final shape includes brick shapes with parallelepiped shapes, the shape of a polygon pillar, (the shape of a hexagon pillar, an octagonal pillar, etc.), tetrahedron shape with four triangular planes, etc. The material of a fibrous substrate is usually paperboard.
Furthermore, in the paper packaging container of a gable top shape (roof type), paper packaging material is cut in predetermined shape for the blanks sealed in the container lengthwise direction, after sealing the bottom of the blanks by the filling machine, cows milk, juice, or other drinks are packed from an top opening, the upper part is sealed, and the product container is obtained. In such packaging material, the appearance design of a packaging container product is printed on the surface.
The laminating packaging material used for the conventional paper packaging container product includes the following: A low density polyethylene (LDPE)/printing ink layer/paper substrate layer (fibrous carrier layer)/LDPE/aluminum foil (Al layer, gas barrier layer)/LDPE/LDPE, LDPE/printing ink layer/paper substrate layer/LDPE/LDPE, a printing ink layer/LOPE/paper substrate layer/LDPE/LDPE and LDPE/printing ink layer/paper substrate layer/LDPE/aluminum/polyester (PET). The above is also actually used widely currently.
In manufacture of the above-mentioned laminate for packaging, generally, the raw-paper roll of a paper substrate layer is carried to a press, the printed paper printed to the raw-paper side is again wound around a roll shape, subsequently to a raw-paper side, with an extrusion laminator, molten polyolefines (for example, LDPE etc.) are extruded from an extruder, and, if the gas barrier layers (aluminum foil etc.) other than a raw paper are included a gas barrier layer is also laminate-coated. When laminating the above gas barrier layers or adding the functional layer of further others, not all layers are laminated at once, partial laminate are prepared separately, respectively, for example, in-line, and these partial laminates are laminated further and the final laminate is obtained.
However, LDPE used is a high-pressure-process low density polyethylene. The low-molecular-weight component included in the high-pressure-process low density polyethylene bleeds to the face to be laminated of an opposite side in a temporary roll shape. Even if other layers are laminated to a surface to be laminated, a good adhesive property is not guaranteed. The low-molecular-weight component bleeds to the content of the liquid food in the paper container after container-izing and filling, and when preserving at a long period of time, the taste of liquid food deteriorates.
On the other hand, the laminate for paper containers which uses a linear low density polyethylene (LLDPE) for the innermost layer of the laminate for packaging is proposed (JP 62-78059A, JP 60-99647A, etc.). The LLDPE is very excellent in an impact strength, tear strength, cold brittleness, heat-sealing strength, hot tag performance, etc. However, how to solve the above-mentioned problem of the LDPE is not shown.
On the other hand, the paper container including in the innermost layer of the laminate for packaging the ethylene alpha olefins copolymer (the so-called metallocene PE, mLLDPE) which polymerized according to the metallocene catalyst is proposed. (JP,7-148895,A, JP,8-337237,A, JP,9-29868,A, JP,9-52299,A, JP,9-76435,A, JP,9142455,A, JP,9-86537,A, JP,9-76375,A, etc.). The metallocene PE is good for a low-temperature sealability, the workability of a film, and the health performance by a molecular weight distribution being narrow. As for the metallocene PE, the application to a container is known. (See WO 93/08221, Magazine “plastics” Vol. 44 No. 1 P 60, Magazine “chemistry economy” Vol. 39 No. 9 P 48, Magazine “plastics” Vol. 44 No. 10 P 83.) However, even though Metallocene PE has the low concentration of a low-molecular-weight component. In all the various process conditions in the production process of the actual laminate for packaging, the bond strength between the constitution layers of the laminate for packaging cannot be improved to practical strength.
When liquid food is fruit juice of citrus fruits etc., the non-scalping for perfume and tasty and an oxygen barrier are needed. In the liquid food, oxygen penetrates through the wall of carton and, for the reason, those nutritional value is lost. In order to reduce penetration of the oxygen to carton and to minimize degradation of nutrients, such as vitamin C, usually the layer of an aluminum foil is added to lamination material (laminate).
Although the aluminum foil is effective as a barrier material, the various attempts of development of a practical alternative to an aluminum foil are made due to the concern on the environment by the use. The alternative is provided with the outstanding barrier properties over oxygen, gas, and aroma, and can be easily scrapped after use.
Using the vapor deposition layer of an inorganic oxide for the packaging material for paper containers as an alternative which changes to an aluminum foil is proposed conventionally. (See JP,5-28190,Y, JP,8-500068,A, JP,6-93120,A). By the packaging material which has such a gas (oxygen) barrier, the paper container which has a non-scalping or a quality preservability can be offered. However, the junction performance of the vapor deposition layer surface of an inorganic oxide, and the adhesives for a lamination or a resin is not good. In all the various process conditions in the production process of the actual laminate for packaging, the adhesive strength between the constitution layers of the laminate for packaging is not practical.
In addition, in order to prevent oxidation degradation of a content food and increase of a microorganism by the oxygen which exists in the packaging, or in the oxygen which permeates from the outside, means to remove the oxygen inside the packaging are provided conventionally. For example, the technique of scavenging oxygen to packaging material using the synthetic resin which kneaded L ascorbic acid and the ferrous ion compound (JP,4-31949,Y) is known. Also known is packaging material which prevents the heat deterioration of the oxygen scavenger at the time of manufacture and the bleed out of oxygen scavenger, by having the adhesives layer which mixed ascorbic acid (derivative) and the transition-metal compound of a reaction accelerator (JP,6-190960,A), and packaging material which prevents the heat damage of the oxygen scavenger at the time of manufacture, and the bleed out of oxygen scavenger by spraying and adhering of the deoxidant and/or a desiccant to the adhesives layer on a substrate sheet, and coating of a protection layer (JP,60-10708,U).
However, in conventional packaging material aiming at quality retention of a contents product, the suitable packaging material for quality retention is not proposed to the liquid food kept and sold under warming, for example, a coffee drink, oolong tea, etc. With the above-mentioned conventional technique, various material is listed as oxygen scavenger. For several weeks or several months, under the condition of warming, when kept and sold within an automatic vending machine or a hot chamber, suitable packaging material (especially packaging material made of paper (fibrous)) is not suggested conventionally. The method of manufacturing of the good laminate for packaging without the delamination between layers is not indicated.
In this invention, the purpose aims at offering the manufacturing method of the good laminate for packaging without the delamination between layers based on an above-mentioned background. The purpose is offering the packaging laminating material which has strong layer adhesion in an automatic vending machine or a hot chamber under the condition of warming for the purpose of quality retention of the liquid food kept and sold, for example, a coffee drink, oolong tea, etc. for several weeks to several months. The purpose is offering the method of manufacturing of the laminate for packaging which converts efficiently, effectively and easily in manufacture of laminating package material.